Organization of the North Atlantic Treaty Organisation (NATO) was created after the signing of the agreement in Washington on 4 April 1949 and is now an alliance of 28 member countries from North America and Europe, which have pledged to meet guidelines such agreement. Twelve states founder of the said organization, namely: Belgium, Denmark, Iceland, Luxembourg, Norway, United Kingdom, Canada, France, Italy, Netherlands, Portugal, United States. NATO over the years of the Cold War and the tensions between the Soviet Union and the United States and other Western countries held various tests and the preservation of peace in Europe. In the meantime, since its foundation in six rounds of enlargement has joined sixteen states including Croatia in 2009. Over time, the alliance changed and going through the continual transformation of all aspects of action, and he took over new tasks of which are also some from outside the Euro-Atlantic area. NATO has acted and continues to act on various missions and operations and to Macedonia, Afghanistan, Iraq, Sudan, Bosnia and Herzegovina and in Kosovo. NATO embodies the bond linking North America and Europe in a unique defense and security alliance.